Hydraulic positive drive pump or motor



Nov. 29, 193 8. E. K. 'BENEDEK 2,133,018

HYDRAULIC P OSITIVE DRIVE PUMP R MOTOR Filed March 12, 19:55 6 heets-Slieet 1 50 a! w M J G I %2{\\ )8} 10/7 I! I /J {I 134 4 V 1 x 51 51 x 3 @6 V I H H!!! ax 40 C F151 ELEKKEENEUEK W g 7 Filed March 12, 1955 Nov. 29, 1938. E K BEN-EDEK 2,138,018

HYDRAULIC POSITIVE DRIVE PUMP OR MOTOR Filed March 12, 1935 6 Sheets-Sheet 6- Patented Nov. 29, 1938 UNITED STATES PATENT OFFICE 2,138,018 HYDRAULIC POSITIVE DRIVE PUMP OR MOTOR Elek K. Benedek, Bucyrus, Ohio Application March 12, 1935, Serial No. 10,691

8 Claims.

This invention relates to variable delivery, radial piston, hydraulic pumps and motors particularly of the rotary reactance high pressure type, the principal object being to efiect a positive driving relation between the primary rotor or barrel and the reactance rotor for the purpose of relieving the pistons from substantially all stresses and reactions except direct radial thrusts.

Heretofore, in pumps and motors of this character, the customary practice has been to utilize the pistons themselves as the driving connection between the primary and reactance rotors, either by frictional or positive connection between the pistons and the reactance rotor. Necessarily, this subjects the piston and cylinder walls to the tangential forces necessary to transmit the working torque from one rotor to the other. Since the pistons operate under comparatively high fluid pressures, they must fit very snugly and with a minimum of clearance in their respective cylinders for efiiciency in op,- eration. Under these coexisting forces, the pistons and bore walls aresubjected to high frictional resistance with resultant rapid wear. Again in pumps of this character these conjoint compressive and torque transmitting forces result in the development of undue heat and decrease in eiiiciency.

As set forth in my copending application Ser. No. 3,455, filed January 25, 1935, wherein disadvantages of such pumps and motors are described more fully, such pu mps may well be described collectively as coupling pumps, the exa pression being used in its literal sense inasmuch as the sole mechanical'coupling for transmitting torque between the rotors are the pump mechanisms, includingv the pistons, cylinders and crosshead assemblages.

-10 One type of coupling pumps includes those utilizing the flexible piston coupling. In this type there is a rocking action between the piston head and its push stem, which action, during the maximum load transmitting period, causes the driving rotor to lead the driven rotor with resultant development of localized torsional stresses. Again, upon sudden relief of the load, the driven rotor tends to overrun the impelling 5U rotor, with the result that torsional oscillation between the two rotors developes, rendering the pumps noisy and proper timing difiicult. Often this action results in the cylinder ports being in the center line of the closing bridges of the valve pintle while the pistons are materially out of dead center positions and consequently not properly cooperating with the pintle ports.

With these disadvantages in mind, an object of the present invention is to provide a pump or motor of this character in which the torque 5 transmitting function of the radial piston assemblages is entirely eliminated and in which, instead, the primary and reactance rotors are positively drivingly connected through an efiicient mechanical coupling. 10

Another object is to maintain proper valving relation between the pintle ports and the cylinder ports by maintaining proper synchronization of the rotors.

Another object is to provide a more effective 15 piston mounting and reduce the size and weight of various reciprocating portions of the piston assemblages whereby centrifugal forces and forces resulting from inertia of the piston assemblages during reciprocation are reduced. 20

Another object is to provide a longer and more efiective guide for the pistons so as to minimize side wear between pistons and their cylinder walls.

A more specific object is to provide an improved secondary rotor which may be readily manufactured and assembled while retaining the characteristics by which the reactance thrusts thereon are uniformly distributed over the .secondary rotor housing.

Other objects and advantages will become apparent from the following specification wherein reference is made to the drawings in which Fig. 1 is a vertical sectional view of a pre;

tor;

Fig. 2 is a cross sectional view of the pump or motor taken on a plane indicated by the line 2-2 of Fig. 1;

Fig. 3 is a sectional view similar to that of Fig. 2 illustrating a modified connection between the pistons and reactance rotor;

Fig. 4 is a vertical cross sectional view taken on a plane indicated by the line 44 or la-4a of 1;

Fig. 5 is a vertical cross sectional view taken on the plane indicated by the line 5-5 of Fig. 1;

Fig. 6-is a vertical sectional view taken on a plane indicated by the line 66 in Fig. '7, illustrating a slightly modified form of coupling between therotors;

Fig. '7 is a longitudinal vertical sectional view of the coupling means between the rotors and. is taken on a plane indicated by the line of F g.- 6; g

ferred embodiment of the present pump or mo- 35 Fig. 8 is a perspective view of the semi-floating coupling element illustrated in Figs. 1 to 4 respectively;

Fig. 9 is a fragmentary side elevation showing one type of groove for operatively connecting the pistons to the reactance rotor;

Fig. 10 is a view similar to that of Fig. 9 illustrating a slightly modified form of connection between the pistons and reactance rotor;

. Fig. 11 is a fragmentary longitudinal'sectional view of the modified reactance rotor and is taken on a plane indicated by the line lI-l I'in Fig. 3; Fig. 12 is a fragmentary sectional view of the main elements of the reactance rotor taken on a plane indicated by the line l2l2 of Fig. 10;

Fig. 13 is a fragmentary sectional view similar to Fig. 12 and is taken on a plane indicated by the line l3-l3 in Fig. 5;

Fig. 14 is a fragmentary plan view of the primary rotor showing the manner of guiding the piston crosshead therein;

Figs. 15 and 1 6 are a plan view and elevation respectively of one of the pistons of the present invention;

Fig. 17 is a full scale elevation of a capillary Figs. 24 and 25 are a longitudinal sectional view and an end elevation respectively of a spacing element for the reactanegrotor parts}.-

Referring to the drawings, the pump or motor mechanism is mounted within a rigid casing I, closed at its ends by rigid-end covers 2 and 3 respectively. Rotatably mounted-within the easing is a primary rotor 4 having a dead end axial bore 4a in which is received a valve pintle 5. The pintle is supported by one end in a suitable rigid hub. portion in" the end cover 2 and protrudes therefrom inwardly, the protruding portion being received in valving relation in the dead end valve bore 4a of the rotor 4. Capillary needle bearings are provided near each end of the valve portion of the pintle and cooperate with the walls of the rotor bore for resisting hydrostatic deflection of the pintle. For rotatably supporting the rotor 4 within the casing, a set of anti-friction bearings 6, mounted in an internal annular recess in the cover plate 3, are provided,

the inner race of bearings being securely mounted on a hub portion at the corresponding end of the rotor 4. The bearings 6 are arranged to resist outwardly axial thrusts as well as radial thrusts.

A driving shaft 1, preferably formed integrally with the rotor, extends through the cover 3. At the opposite end of the rotor from the bearings ,6 is a thrust washer 8 which abuts an annular end wall portion of the rotor and a complementary end wall of an inwardly extending boss formed on the cover 2, thus cooperating with the bearings 6 for maintaining the rotor 4 in fixed position axially with respect to the pintle to prevent undue wear.

Intermediateits ends, the rotor is provided with a radially enlarged portion in which are provided a series of circumferentially spaced cylinders 9, each cylinder having a valve port In cooperable successively with the valve ports II and I2 of the pintle. For the purposes of illustration, the pintle port H is considered the pressure port, the pintle port [2 being considered the suction or, in the case of a motor, the low pressure port. The'pintle is providedwith the customary longitudinal passages l3 and I4, for con ducting the fluid to and from the operating mechanism of the pump in the usual manner, the passages l3 communicating with the pintle port II and the passages l4 communicating with the pintle port l2.

Carried by the rotor and arranged one in each of the cylinders 9 are radially reciprocable pistons l5, each of which is provided with an enlarged head l6 having a bore extending transversely of the path of rotation and preferably parallel to the axis of the rotor 4. Mounted respectively within the bores of the heads I 6 are crosspins H, the ends of which pins protrude from the head IS in opposite directions for engagement with the reactance rotor, later'to be described. Capillary anti-friction needle bearings Ha are provided between each crosspin and the walls of the head bore in which received, for insuring the maintenance of proper lubrication therein under the centrifugal forces resulting from operation of the pump, for providing-a large bearing surface for transmitting radial thrusts to the pistons, and for reducing the radial length and the weight of the piston assemblage. The needle bearings extend substantially the full length of the head bore for preventing rocking of the crosspin therein.

As better illustrated in Fig. 14, the rotor 4 has a radial flange I8 which is provided with a series of radial notches l9, corresponding to the number of pistons. The walls of the notches are spaced forwardly and rearwardly in the direction of travel and are arcuate to accommodate the crossheads I6 of the pistons, the leading and trailing walls of which are complementary thereto. Thus each piston, insofar as the rotor affects its operation, is free to be rotated about its own axis.

The reactance assembly comprises an annular reactance housing 20 which, as better illustrated in Fig. 2, is provided with opposite aligned and parallel slide bearing surfaces 2| cooperable with corresponding bearing surfaces in the casing I for supporting the reactance housing therein with its axis parallel to the axis of the primary rotor 4. Suitable adjustment rods 22 are connected to the reactance rotor housing and extend through bores in the casing I to the outside for shifting the housing to different positions along the bearing surfaces so that it may be adjusted to positions coaxial with or with its axis parallel and eccentric to the axis of the primary rotor, thus varying the eccentricity of the rotors and controlling the length of stroke of the pistons.

At its inner face, near the-margins thereof, the housing 20 carries coaxial equal diameter sets of anti-friction bearings 24 through the'medium of which the reactance rotor, designated generally as 25, is supported, the reactance rotor being at all times coaxial with the housing 20. The reactance rotor must necessarily withstand and transmit to the housing 20 the entire hydrostatic reactions resulting from compression of the operating fluid, the centrifugal forces and other 75 dynamic forces resulting from operation. It must therefore be strong, durable, and highly resistant to wear. Furthermore, since the valving operation is dependent upon accuracy in the position of the parts of the reactance rotor which cooperate with the piston crosspins II, the parts, likewise, should be accurately formed.

Heretofore it has been the practice to form reactance rotors of this character in circular seg-,

ments and then fit the same together to form the annular rotor. Necessarily this results in an insecure structure, and the thrusts transmitted thereto by the pistons tend to be concentrated on the particular segment against which the pistons are reacting. Accordingly, this thrust is concentrated on a limited portion of the reactance housing 2|], or the casing, as the case may be.

In order to provide an inexpensive and practical rotor of the accuracy desired while, at the same time, forming the reactance of suitably durable material, and to provide for more uniform distribution of the reactance thrusts and other forces transmitted thereto, the rotor is made in a plurality of parts assembled in a different manner than heretofore to form a substantially unitary structure. The present reactance rotor has been made to meet not only these requirements but to permit ease in assembly, installation, and repair or service.

Referring first to Figs. 1 and 13, the rotor 25 comprises two annular elements, or rings, 30 and 3|, which are spaced apart axially a sufficient distance to snugly accommodate the piston crossheads therebetween. The rings 30 and 3| are provided at their adjacent faces with chordal slots 32 and 33 respectively, the slots being aligned with and opening toward each other. The radially inner and outer walls of the slots 32 and 33 form the operating cams for the pistons and receive and accommodate the protruding ends of the crosspin ll of the pistons. The pins H are free to rotate about their own axes during radial reciprocation of the pistons. The slots are of sufficient depth axially of the rings to hold the crosspins in substantially fixed position axially or to permit only slight axial shifting or floating thereof.

For mounting the rings 30 and 3|, annular reactance elements 34 and 35 are provided. S nce each of the elements 3 and 35 are the same and cooperate in a similar manner with the one of the rings 3|] and 3| with which associated, the element 34 only will be described. 'It shou d be noted, however, that the elements 34 and 35 are oppositely positioned with respect to each other.

The element 34 comprises an axially extending annular hub portion 36, carrying at the end adjacent the ring 30 a radially extending annu ar flange 31, the flange 31, in turn, being provided with an axially extending annular flange 38. The flange 38 protrudes from-the flange 31 in a direction opposite from the hub portion 36. The inner radial face of the flange 31 and the inner annular face of the flange 38 are accurately finished so as to receive and accurately fitthe adjacent radial face and outer annular face of the ring 30 respectively. The flange 38 preferably terminates flush with the face of the ring 30 adjacent the pistons and thus likewise forms part of the guideway for the piston crossheads IS. The element 35 correspondingly accommodates the ring 3|. At 'circumferentially spaced points, the elements 34 and 35 and rings 30 and 3| are provided with aligned transverse bores for accommodating bolts 39 by which the elements and rings are secured together. Suitable spring spacers 40 are disposed between adjacent faces of the rings 3|) and 3| for effecting proper spacing thereof and to permit clamping engagement between the rings and the elements 34 and 35 when assembled. Thus the rings and cooperating elements are drawn together to form a circumferentially continuous and substantially unitary reactance rotor.

It is apparent that the rings 38 and 3| I may be made of the desired material to withstand the wear and hardened to the degree necessary to maintain accuracy. Furthermore, all of the parts comprising the rotor are readily accessible for the necessary machining operations in manufacture. Equally important, however, is the fact that the resultant reactance rotor is continuous circumferentially and therefore any hydrostatic reactances or other stresses imposed thereon are transmitted and distributed more uniformly to the reactance housing 20 and not concentrated in any limited circumferential portion thereof.

In the preferred embodiment of the invention. especially in those instances wherein the rotors are drivingly connected other than by" means of the pistons, the slots 32 and 33 are'chordal, as described. to compensate for the instantaneous tangential component of eccentricity with its resultant lead and lag in the relative angular position of the rotors. Necessarily, therefore, any hydrostatic reactance is delivered to the crosspins ll radially of the pistons only and the pistons relieved from any transverse or tangential forces tending to cause them to bind in the cylinders l5.

By providing a direct connection between the primary rotor and the reactance rotor, a number of heavier working parts may be eliminated and the radius to the point of application of the reactance is reduced. These changes are accompanied by a corresponding reduction in the centrifugal forces and dynamic inertia of the working parts which necessarily accompany high speed operation.

Referring then to the coupling by which the reactance rotor and primary rotor are drivingly connected, the primary rotor is provided at opposite ends with hubs 50, each of which is preferably rectangular. Since both hubs and couplings are the same, one only will be described in detail. At diametrically opposite sides of its axis of rotation each hub has parallel external bearing sur-' faces 50a and 581). These surfaces are spaced equidistant from the axis and are preferably planar. ing annular connecting element 5|, having spaced parallel internalbearing surfaces 5|a and 5H), complementary to and cooperating with the hub surfaces 50a and 50b respectively for mounting the element 5| for oscillation relative to the hub in a straight path parallel to the faces 50a. and 50b of the hub. The element 5| is also provided with external parallel bearing surfaces 5|c and 5 Id arranged at diametrically opposite sides of the axis of the elementfrom each other and positioned to define planes located at right angles to the planes of the surfaces 5|a and 5|b. Correspondingly, the hub 36 of the element 34 is provided with internal bearing surfaces 350 and 36d cooperable respectively with the surfaces 5|c and 5|d for mounting the element 5| for reciprocatory movement along the surface 380 and 36d. The bearing surfaces 360 and 36d likewise are nec- Surrounding the hub 58 is a semi-floatessarily at right angles to the surfaces 5|a and" 75 lb. The passage through the element 5| is of greater dimension in the direction of the surfaces 5|Ia and 50b than the corresponding dimension of the hub 50 of the rotor 4 to permit the required limited reciprocation of the coupling element with respect to the hub 50. Correspondingiy, the central passage in the hub 36 of the element 34 is of greater dimension in the direction parallel to the surfaces 360 and 36d to permit the required reciprocation of the element 5| therein relative to the hub. These clearances necessarily are determined by the maximum eccentricity of the rotors. of illustration, that the primary rotor 4 is driven and the reactance rotor is set coaxial therewith the hub 50, the element 5| and the reactance rotor hub 36 will be coaxial. Referring to Fig. 4, upon setting the rotors in eccentric positions,

however, the radial component of the eccentricity will be compensated for by shifting of the element 5| with respect to the hub 50. The tangential component of the eccentricity will be compensated for by shifting of the element 5| relative to the hub 35. In 90 degrees from the position described, the radial component will be compensated between the element 5| and the reactance rotor and the tangential component between the element 5| and the hub 50. In intermediate positions, the components of eccentricities will be compensated partially by each. All of these coacting bearing surfaces are of sufficient extent to prevent rotation of the element 5| relative to the rotors and to assure the same angular velocity of the rotors with respect to their respective axes of rotation. Thus the transmission of all the torque is accomplished without imposing any torsional driving stresses on the piston assemblages.

In high pressure and high speed operation, terrific reactance stresses are developed which would tend to cause binding of the hubs and the element 5|. Furthermore, the centrifugal stresses would tend to discharge oil therefrom so rapidly as to render lubrication ineflicient. For insuring proper shifting of the element 5| and for reducing frictional resistance between the element 5| and the cooperating hubs, sets of capillary needle bearings are provided, one set being provided between each set of cooperating bearing surfaces. For this purpose troughs 60 are provided, preferably in the surfaces 5|a and 5|b, these troughs being positioned centrally of the bearing surfaces in thedirection of tangential travel and terminating a sufficient distance from the ends of the bearing surfaces so as not to expose the bearings beyond the cooperating surfaces 50a and 50b of the hub 50 when the element 5| is shifted to its extreme positions. Free capillary roller needle bearings Bl are provided and disposed transversely of the direction of movement of the cooperating surfaces and are of sufficient diameter to provide the bearing relation between the flat bottoms of the troughs 60 and the cooperating bearing surfaces of the hub 50.- The sets of bearings terminate in spaced relation to the ends of the troughs in the direction of travel so that the bearings may roll individually and maintain therebetween a capillary oil film. Such a film not only insures proper lubrication and spacing of the bearings but is Assuming, for purposes For holding the bearings" 2,188,018 Troughs 62 are provided in the outer bearing The action of the needle bearings is illustrated in Figs. 20 to 22, inclusive, which show the intermediate and both extreme positions of the surfaces 5|la and 5|a. It should be noted the surfaces themselves form the races and containers and ample room is allowed in the direction of relative travel of the surfaces to permit the bearings to roll individually.

Referring briefly to Fig. 10, a ring 65 corresponding to the rings 30' and 3| is shown as provided with a short chordal slot 66, the advantages of which have heretofore been delineated.

In Figs. 3 and 11, rings 30' and 3|, corresponding to rings 30 and 3| are shown as provided with circumferential slots 32' and 33' corresponding to slots 32 and 33.

Referring specifically to Figs. 6 and '7, a modifled coupling suitable for lower pressures and speeds is illustrated, the parts of the pump therein corresponding to those heretofore described, being designated by corresponding primed numerals. In this installation the hub 36' is provided with an internal axially extending annular shoulder which is circular, and separately formed and treated thrust plates 10 andll having outer surfaces complementary to the internal shoulder of the hub are provided. The plates 10 and II are secured in position by suitable bolts 12 and their inwardly exposed faces are plane and parallel to each other. On the hub 4' opposite parallel faces 14 and 16 are provided. The element 5| is replaced by an annulus 5| of circular cross section having an internal axially extending circumferential wall which is likewise circular. Thrust plates 11 and 18 complementary on their outer surface to the internal wall of the elem'ent 5| are secured thereto in, diametricallygopposite positions from each other by bolts 19. The inwardly exposed faces'8li-and 8| of these plates are plane surfaces parallel with respect to each other and cooperable with the surfaces 14 and 16 of the hub,

for permitting the necessary reciprocatory motion between the element 5| and the hub Q; Obviously, where low pressures and speeds permit,

this coupling element is preferred, inasmuch as all of the parts can be made separately 'anddf the particular metal most desirable, and readily assembled to form a substantially unitary structure.

It is apparent from the foregoing description that a high efliciency of hydrostatic reactance is provided between the reactance rotor and the pistons without subjecting the pistons to driving torque forces. Furthermore, the mass of all rotating parts is greatly reduced and so positioned as to lie close to the axis of rotation. As a resultthe centrifugal forces and dynamic inertia of the reciprocating or oscillating parts are greatly reduced so asnot to detract from the efficiency and smoothness of operation. Again, by the provision of capillary anti-friction needle bearings, oil films are maintained between the coupling element and the hubs and between the piston crosspins and the cooperating bearings inthe crossheads against the effects of general and localized centrifugal forces and thrust pressures. By the provision of corresponding needle bearings between the valve pintle and primary rotor, unbalanced hydrostatic reactance tending to deflect the pintle from its normal coaxial position with the rotor are so reduced that substantially perfect alignment and hydraulic fit is maintained at all times throughout the operation. Lastly, it will be apparent from the drawings and description that each of the elements of the structure are extremely simple and consequently may readily be manufactured economically without the necessity of highly specialized castings and machines. 3

The synchronous drive in combination with the single crosspin and chordal groove connection between the pistons and reactance is disclosed and claimed in my copending divisional application Serial No. 228,136 filed September 2, 1938.

Having thus described my invention,

I claim:

1. In a hydraulic radial piston pump or motor of the character described, a primary rotor having a circumferential series of radial piston assemblages, and having a reduced hub portion at one side of the plane of said assemblages, a reactance rotor for the piston assemblages having an annular h'ub positioned in radial alignment with the hub of the primary rotor and in spaced relation radially therefrom, said rotors being eccentric to each other, the radial inward hub having diametrically opposite external plane parallel bearing faces, said other hub having diametrically opposite internal plane parallel bearing faces positioned at right angles to those of the other hub, and a rigid annular coupling element surrounding the inner one'of said rotor hubs and lying wholly within the axial limits of the rotors and having internal plane bearing faces cooperable with those of the inner rotor hub and external plane bearing faces at right angles to its internal plane bearing faces and cooperable with those of the outer hub, said bearing faces of the rotor hubs and element mounting the element for concurrent oscillations in two lineal paths disposed at right angles to each other, whereby the eccentric rotors are positively drivingly connected to each other.

2. In a rotary radial piston pump or motor of the character described, including a primary rotor having a set of circumferentially spaced piston assemblages, and a reactance rotor for the piston assemblages and eccentric relative to the primary rotor, hubs on the primary rotor, one at each side of the plane of the piston assemblages, hubs on the reactance rotor positioned in radial alignment with the primary rotor hubs respectively in radial spaced relation, and semifloating coupling means interposed one between each pair of hubs for driving one by the other, each of said coupling means being connected at its outer surface to one of the hubs with which it is associated for rotation therewith and oscillation in a lineal path relative thereto and connected to the other of the hubs with which associated for rotation therewith and oscillation relative thereto in a lineal path at right angles to the aforesaid lineal path and said elements lying wholly between the axial limits of the rotors.

3. In a hydraulic 'pump or motor of the rotary radial piston type, including a primary rotor, a plurality of piston and cylinder assemblies carried thereby, a reactance rotor cooperable with the assemblies for reciprocating the same upon concurrent rotation of the rotors, said rotors being disposed eccentrically'with respect to each other and one of said rotors being in surrounding relation to the other, the outer one of said rotors having an annular hub portion with annular arcuate internal walls, thrust blocks having arcuate outer surfaces abutting said arcuate walls and having internal planar surfaces, means securing the blocks to said annular hub portion with the planar surfaces diametrically opposite from each other and parallel to each other, a planetating connecting element comprising a rigid ring having outer plane parallel bearing surfaces complementary to the plane faces of the blocks, diametrically opposite thrust blocks fitting within said ring and secure-d to the inner arcuate surface thereof and having inner plane parallel bearing surfaces at right angles to the outer plane parallel bearing surfaces, and the inner rotor having a, hub portion extending into the ring and provided with plane diametrically opposite parallel surfaces in engagement with the inner plane bearing surfaces of the ring.

4. In a hydraulic pump or motor comprising primary and secondary rotors eccentrically dis posed with respect to each other, radially aligned hubs on the rotors, respectively, one of said rotorhubs being in surrounding relation to the other, and radially spaced therefrom and providing a radial clearance space between the hubs, piston and cylinder assemblies carried by one rotor and cooperating'with the other rotor for reciprocation thereof, valve means for the assemblies, and universal planetating coupling means drivingly connecting the rotors through the hubs for synchronous rotation, said planetating coupling means being accommodated in the radial clearance space between the hubs and terminating axially of the rotors within the axial limits of the rotors.

5. In a rotary, radial piston pump or motor including rotatable inner and outer rotors eccentrically disposed with respect to each other, piston and cylinder assemblies carried by one of the rotors and operated by the other rotor upon concurrent rotation of the rotors, valve means for the assemblies, the outer rotor having a portion in surrounding and radially spaced relation to a portion of the inner rotor, external anti-friction bearings on said surrounding portion of the outer rotor and supporting the outer rotor for rotation, the outer rotor having internal parallel bearing surfaces in the said surrounding portion at opposite sides of its axis of rotation and aligned radially of the rotors with said anti-friction bearings, the inner rotor having external parallel plane bearing surfaces on its surrounded portion at opposite sides of its axis of rotation, a rigid annular planetating element having a pair of internal plane bearing faces and a pair of external plane bearing faces in sliding contact with the pair' of external and the pair of internal bearing faces of the rotors, respectively, for oscillation therealong.

6. In a rotary, radial piston pump or motor including rotatable inner and outer rotors eccentrically disposed with respect to each other, piston and cylinder assemblies carried by one of the rotors and operated by the other rotor upon concurrent rotation of the rotors, valve means for the assemblies, the outer rotor having a por- 1 -external parallel plane bearing surfaces on its surrounded portion at opposite sides of the axis of rotation from each other and extending at right angles to said internal plane bearing surfaces, a rigid annular planetating element having a pair of internal plane bearing faces and a pair of external plane bearing faces on its inner and outer periphery, respectively, and in sliding contact, respectively, with the pair of external and the pair of internal bearing faces of the rotors, said element being disposed close to said external anti-friction bearings which support the inner rotor at the end of said surrounded portion, and said element normally being aligned axially of the rotors therewith and being substantially the same in dimension parallel to the plane of the external anti-friction bearings of the said end of the inner rotor as the pitch diameter of the said external anti-friction bearings of the inner rotor.

7. In a rotary, radial piston pump or motor including rotatable inner and outer rotors eccentrically disposed with respect to each other, piston and cylinder assemblies carried by one of the rotors and operated by the other rotor upon concurrent rotation of the rotors, valve means for the assemblies, the outer rotor having a portion in surrounding and radially spaced relation to a portion of the inner rotor, external antifriction hearings on said surrounding portion of the outer rotor and supporting the outer rotor for rotation, and rigid planetating coupling means drivingly connecting the rotors through said portions and disposed in a radial space therebetween and aligned radially of the rotors with said anti-friction bearings. v

8. In a hydraulic pump or motor of the rotary radial piston type including a primary rotor having a plurality of circumferentially spaced radial cylinders, piston assemblages respective to the cylinders, and a. reactance rotor eccentric to the primary rotor and cooperable with the pistons for reciprocating the same upon concurrent rotation of the rotors, one of said rotors including a 10 hub having spaced external plane parallel bearing faces, a. semi-floating rigid annular element having spaced parallel internal plane bearing faces on its inner periphery and complementary to the said faces of the hub, and having its cengtral opening greater in length in the direction parallel to said surfaces than the hub. whereby planar oscillation of the element relative to the hub is effected, said element having additional spaced parallel external plane bearing faces on 

